PIEZOELECTRIC DEVICES AND METHODS FOR MANUFACTURING SAME

• US 20100201221A1
• Filed: 02/10/2010
• Published: 08/12/2010
• Est. Priority Date: 02/10/2009
• Status: Active Grant

• Current Assignee: Nihon Dempa Kogyo Company Limited
• Original Assignee: Nihon Dempa Kogyo Company Limited
• Inventors: Inoue, Takahiro, Saito, Takefumi, Ichikawa, Ryoichi, Umeki, Mitoshi
• Granted Patent: US 8,227,958 B2
• Time in Patent Office: Days
• US Class Current: 310/312
• CPC Class Codes: H03H 2003/0492 during the manufacture of a tuning-fork
• CPC Class Codes: H03H 3/04 for obtaining desired frequency or temperature coefficient
• CPC Class Codes: H03H 9/1035 the enclosure being defined by two sealing substrates sandwiching the piezoelectric layer of the BAW device
• CPC Class Codes: H03H 9/21 Crystal tuning forks
• CPC Class Codes: Y10T 29/42 Piezoelectric device making

Abstract

An exemplary piezoelectric vibrating device includes a piezoelectric frame that supports and surrounds a tuning-fork type piezoelectric vibrating piece having a pair of vibrating arms. The device also includes a lid and a package base that are siloxane-bonded to the frame. The lid defines at least one frequency-adjustment hole extending through the thickness dimension of the lid from an inner major surface thereof (facing the frame) to an outer major surface of the lid. The package base defines at least one through-hole electrode passing via a respective electrode through-hole through the thickness of the base from an inner major surface thereof (facing the frame) to the outer major surface thereof. The electrode is connected to the piezoelectric vibrating piece. The lid and base include external electrodes, made of an electrically conductive material, that cover the through-holes and frequency-adjustment hole(s).

Claims

1. A piezoelectric device, comprising:

a piezoelectric frame comprising a frame portion and a tuning-fork type piezoelectric vibrating piece, including multiple vibrating arms and at least one electrode, surrounded by and attached to the frame portion, the piezoelectric frame including a first major surface and an opposing second major surface;

a lid having a thickness, an outer major surface, and an opposing inner major surface, the inner major surface being bonded to the first major surface of the piezoelectric frame, the lid defining at least one frequency-adjustment hole passing through the thickness of the lid from the inner major surface to the outer major surface thereof;

a package base having a thickness, an outer major surface, and an opposing inner major surface, the inner major surface being bonded to the second major surface of the piezoelectric frame, the package base defining at least one through-hole electrode passing via an electrode through-hole through the thickness of the package base from the inner major surface to the outer major surface thereof, the at least one through-hole electrode providing a respective electrical connection of the electrode on the tuning-fork type piezoelectric vibrating piece to outside the package base; and

at least one external electrode made of an electrically conductive material, the external electrode being connected to a respective electrode in a respective electrode through-hole extending on both the lid and package base so as to cover the at least one electrode through-hole and the at least one frequency-adjustment hole.

2. The piezoelectric device of claim 1, wherein:

each vibrating arm has a distal frequency-adjustment portion; and

each frequency-adjustment hole has a respective location on the lid corresponding to the respective location of the frequency-adjustment portion of a respective vibrating arm.

3. The piezoelectric device of claim 1, wherein each frequency-adjustment hole has a diameter that progressively decreases with increased distance through the thickness of the lid from the outer major surface to the inner major surface of the lid.

4. The piezoelectric device of claim 1, wherein:

each frequency-adjustment hole has a first portion and a second portion that is contiguous with the first portion;

the first portion extends from the outer major surface of the lid to a predetermined connecting point in the thickness of the lid; and

the second portion extends from the inner major surface of the lid to the connecting point; and

at least one of the first and second portions has a diameter that progressively decreases with increased distance to the connecting point from the respective major surface.

5. The piezoelectric device of claim 4, wherein:

the first portion of each frequency-adjustment hole has a diameter that progressively decreases with increased distance through the thickness from the outer major surface of the lid to the connecting point; and

the second portion of each frequency-adjustment hole has a diameter that progressively decreases with increased distance through the thickness from the inner major surface to the connecting point.

6. The piezoelectric device of claim 1, wherein:

each electrode through-hole has a first portion and a second portion that is contiguous with the first portion;

the first portion extends from the outer major surface of the package base to a predetermined connecting point in the thickness of the package base;

the second portion extends from the inner major surface of the package base to the connecting point; and

at least one of the first and second portions has a diameter that progressively decreases with distance to the connecting point from the respective major surface.

7. The piezoelectric device of claim 6, wherein:

the first portion of each electrode through-hole has a diameter that progressively decreases with increased distance through the thickness from the outer major surface to the connecting point; and

the second portion of each electrode through-hole has a diameter that progressively decreases with distance through the thickness from the inner major surface to the connecting point.

8. The piezoelectric device of claim 6, wherein:

each frequency-adjustment hole has a first portion and a second portion that is contiguous with the first portion;

the first portion extends from the outer major surface of the lid to a predetermined connecting point in the thickness of the lid;

the second portion extends from the inner major surface of the lid to the connecting point; and

at least one of the first and second portions has a diameter that progressively decreases with increased distance to the connecting point from the respective major surface.

9. The piezoelectric device of claim 8, wherein:

the first portion of each frequency-adjustment hole has a diameter that progressively decreases with increased distance through the thickness from the outer major surface to the connecting point; and

the second portion of each frequency-adjustment hole has a diameter that progressively decreases with increased distance through the thickness from the inner major surface to the connecting point.

10. A method for manufacturing a piezoelectric device, comprising:

fabricating a piezoelectric frame comprising a frame portion and a tuning-fork type piezoelectric vibrating piece including multiple vibrating arms, the piezoelectric frame having first and second major surfaces, and each vibrating arm including a respective frequency-adjustment portion;

forming at least one electrode on the piezoelectric vibrating piece;

fabricating a lid having an inner major surface, an outer major surface, and a thickness dimension extending between the inner and outer major surfaces thereof;

corresponding to each frequency-adjustment portion, forming a respective frequency-adjustment hole extending through the thickness dimension of the lid;

fabricating a package base having an inner major surface, an outer major surface, and a thickness dimension extending between the inner and outer major surfaces thereof;

corresponding to each electrode on the piezoelectric vibrating piece, forming a respective electrode through-hole extending through the thickness dimension of the package base, each electrode through-hole including a respective electrode extending through the package base to the outer major surface thereof;

bonding the first major surface of the piezoelectric frame to the inner major surface of the lid such that the frequency-adjustment holes are aligned with the respective frequency-adjustment holes, and bonding the second major surface of the piezoelectric frame to the inner major surface of the package base to form a package; and

corresponding to each electrode passing through a respective electrode through-hole, forming a respective external electrode over a sufficient area of the outer major surfaces of the lid and package base to cover at least the respective electrode through-hole and a respective frequency-adjustment hole.

11. The method of claim 10, wherein each frequency-adjustment hole is formed having a first portion and a second portion that is contiguous with the first portion, the first portion extending from the outer major surface of the lid to a predetermined connecting point in the thickness dimension of the lid, and the second portion extending from the inner major surface of the lid to the connecting point.

12. The method of claim 11, wherein the first portion of each frequency-adjustment hole is formed having a diameter that progressively decreases with increased distance in the thickness dimension from the outer major surface of the lid to the connecting point.

13. The method of claim 12, wherein the first portion of each frequency-adjustment hole is formed by machine processing.

14. The method of claim 12, wherein the second portion of each frequency-adjustment hole is formed having a diameter that progressively decreases with increased distance in the thickness dimension from the inner major of the lid to the connecting point.

15. The method of claim 14, wherein the second portion of each frequency-adjustment hole is formed by wet etching.

16. The method of claim 10, wherein the step of forming the frequency-adjustment holes is performed by both machine processing and wet-etching.

17. The method of claim 10, wherein the step of forming the electrode through-holes is performed by both machine processing and wet-etching.

18. The method of claim 17, wherein the step of forming the frequency-adjustment holes is performed by both machine processing and wet-etching.

19. The method of claim 10, wherein each electrode through-hole is formed having a first portion and a second portion that is contiguous with the first portion, the first portion extending from the outer major surface of the package base to a predetermined connecting point in the thickness dimension of the package base, and the second portion extending from the inner major surface of the package base to the connecting point.

20. The method of claim 19, wherein the first portion of each electrode through-hole is formed having a diameter that progressively decreases with increased distance in the thickness dimension from the inner major surface of the package base to the connecting point.

21. The method of claim 20, wherein the first portion of each electrode through-hole is formed by process machining.

22. The method of claim 19, wherein the second portion of each electrode through-hole is formed having a diameter that progressively decreases with increased distance in the thickness dimension from the inner major surface of the lid to the connecting point.

23. The method of claim 22, wherein the second portion of each electrode through-hole is formed by wet etching.

24. The method of claim 19, wherein each frequency-adjustment hole is formed having a first portion and a second portion that is contiguous with the first portion, the first portion extending from the outer major surface of the lid to a predetermined connecting point in the thickness dimension of the lid, and the second portion extending from the inner major surface of the lid to the connecting point.

25. The method of claim 24, wherein the first portion of each frequency-adjustment hole is formed, by machine processing, having a diameter that progressively decreases with increased distance in the thickness dimension from the outer major surface of the lid to the connecting point.

26. The method of claim 25, wherein the second portion of each frequency-adjustment hole is formed by wet etching.

27. The method of claim 10, further comprising the steps of:

irradiating the frequency-adjustment holes with a laser beam to ablate material from the frequency-adjustment portions of the vibrating arms to adjust a vibrating frequency of the vibrating arms;

evacuating the package by subjecting the package to a vacuum; and

sealing the frequency-adjustment holes and the electrode through-holes.

28. The method of claim 27, wherein the sealing step is performed by sealing at least the electrode through-holes with the respective external electrode.